1. Field of the Invention
The present invention relates to an image pickup apparatus and an electronic endoscope system which prevent an unintended value from being written to a register of an image pickup device and a register of a signal processing circuit controlled via a cable.
2. Description of the Related Art
Conventionally, an endoscope system provided with an endoscope is widely known in which the elongated endoscope is inserted into a body cavity or the like to perform observation of an examined site or various treatments. As such an endoscope system, for example, Japanese Patent Application Laid-Open Publication No. 2011-206337 discloses an endoscope system including an electronic endoscope provided with a solid-state image pickup device, and a processor apparatus connected to the electronic endoscope and configured to perform various signal processing for an image pickup signal from the solid-state image pickup device to convert the image pickup signal to image data. Then, the image data converted by the processor apparatus is displayed on a monitor connected via a cable to the processor apparatus.
Although a CCD solid-state image pickup device has been generally used as the solid-state image pickup device mounted on such an electronic endoscope conventionally, a CMOS solid-state image pickup device has also been used recently. The CMOS solid-state image pickup device is provided with registers for storing set values (control data) for driving and reading operations and the like, and the driving and reading operations are performed based on the control data set for the registers. The control data is transmitted from the processor apparatus to the electronic endoscope and set for the registers of the CMOS solid-state image pickup device.
By the way, surgical instruments such as an electrosurgical knife may be used during endoscope observation in the endoscope system, and it may happen that, during transmission of the control data or after the control data is stored in the registers, the control data is rewritten with unintended values by disturbance noise from the electrosurgical knife or the like. When rewriting of the control data due to disturbance noise or the like occurs as described above, an abnormality may occur in the driving and reading operations of the CMOS solid-state image pickup device.
Therefore, in the endoscope system of Japanese Patent Application Laid-Open Publication No. 2011-206337, the control data stored in the registers is superimposed on an image pickup signal outputted from the CMOS solid-state image pickup device to transmit the image pickup signal to the processor apparatus. Then, the endoscope system compares the control data superimposed on the image pickup signal and the control data set for the registers to detect whether rewriting of the control data stored in the registers has not occurred in the processor apparatus.
If detecting that rewriting of a set value has occurred, the endoscope system retransmits the control data from the processor apparatus to the CMOS solid-state image pickup device of the electronic endoscope. That is, if detecting an abnormality of control data stored in the registers, normal control data is transmitted to the registers of the CMOS solid-state image pickup device to reset the control data of registers so that the driving and reading operations of the CMOS solid-state image pickup device is returned to a normal state.
Thus, if the control data set for the registers of the CMOS solid-state image pickup device is rewritten with an abnormal value by influence of disturbance noise or the like, the driving and reading operations of the CMOS solid-state image pickup device can be returned to the normal state by resetting normal control data for the registers.